Hydrogen cyanide has been produced by decomposition of formamide ammoxidation of methane, and so forth. In recent years, the major portion of hydrogen cyanide commercially used has been supplied as a by-product obtained in the production of acrylonitrile by ammoxidation of propylene. However, with substantial improvements in catalysts for the production of acrylonitrile by ammoxidation of propylene, the amount of hydrogen cyanide by-produced has decreased, and it has sometimes become difficult to ensure an adequate supply of hydrogen cyanide for the production of methacrylate by an acetone cyanhydrin process.
Transportation of hydrogen cyanide is difficult and dangerous because of its toxicity. It is, therefore, advisable that hydrogen cyanide be used in a process where it is consumed immediately after it is produced.
The present invention provides a process which can be advantageously employed, for example, in those cases where:
(1) The change of catalyst and so forth in the existing equipment of production of acrylonitrile makes it difficult to ensure supply of hydrogen cyanide to the attached acetone cyanhydrin equipment;
(2) The equipment of production of methacrylate is constructed independently from the acrylonitrile production equipment; and
(3) It is planned to produce hydrogen cyanide which is to be fed to equipment by production of various hydrogen cyanide derivatives.
Various techniques are known for the production of hydrogen cyanide from methanol, including a method where a vanadium/tin oxide catalyst is used (Russian Patent No. 106,226) a method where a tin/antimony oxide catalyst is used (British Patent No. 913,836), a method in which a molybdenum oxide catalyst is used (British Patent No. 718,112 and U.S. Pat. No. 2,746,843), a method in which a catalyst comprising molybdenum oxide and other various elements is used (U.S. Pat. No. 3,911,089), a method in which an oxide catalyst comprising antimony, and iron, cobalt, nickel, manganese, zinc, uranium, or the like is used (JP-B-54-39839 and U.S. Pat. No. 4,461,752) (The term "JP-B" as used herein means an "examined Japanese patent publication"), a method in which a phosphate of manganese, iron, cobalt, nickel, zinc, boron or uranium is used as a catalyst (European Patent Publication No. 121032A), a method in which an oxide catalyst containing manganese or phosphorus is used (U.S. Pat. No. 4,457,905), a method in which an oxide catalyst containing iron, copper and antimony is used (JP-A-58-145617, JP-B-63-16330 and U.S. Pat. No. 4,461,752) (The term "JP-A" as used herein means an "unexamined published Japanese patent application"), and a method in which antimony phosphate is used (U.S. Pat. No. 4,511,548).
These prior art methods, however, are disadvantageous industrially because of the high molar ratio of ammonia to methanol in the feed gas, the use of a large amount of steam, low methanol concentration, and low physical properties of catalysts as typified by marked time-dependent change and poor catalyst strength. Of the known catalysts described above, the Fe-, Cu- and Sb-containing oxide catalyst shown in JP-A-58-145617, JP-B-63-166330 and U.S. Pat. No. 4,461,752 are preferred because of the various advantages it has, but it is still unsatisfactory in terms of activity to a concentrated methanol feed.